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Isern, Alexandra R.

Works: 18 works in 58 publications in 1 language and 122 library holdings
Roles: Author
Classifications: QE472,
Publication Timeline
Publications about Alexandra R Isern
Publications by Alexandra R Isern
Most widely held works by Alexandra R Isern
Proceedings of the Ocean Drilling Program. B : Scientific results ( Book )
in English and held by 82 libraries worldwide
Carbonate platform development off Northeast Australia the importance of paleoceanographic and environmental change by Alexandra R Isern( Book )
1 edition published in 1993 in English and held by 8 libraries worldwide
ODP drilling in the Coral Sea : sealevel variation, fluid flow, and paleoceanography : proposal 510-rev 1 ( Book )
1 edition published in 1997 in English and held by 5 libraries worldwide
ODP drilling in the Coral Sea : sealevel variation, paleoceanography, and fluid flow ( Book )
1 edition published in 1997 in English and held by 4 libraries worldwide
Calcium carbonate and organic carbon accumulation in the Central Equatorial Pacific by Alexandra R Isern( Archival Material )
1 edition published in 1991 in English and held by 2 libraries worldwide
Proceedings of the Ocean Drilling Program. B : Sites 1033-1034 : Scientific results ( Book )
in English and held by 2 libraries worldwide
Stable isotope, seismic sequence boundaries and bioevents in ODP Hole 166-1006A, supplementary data to: Spezzaferri, Silvia; McKenzie, Judith A; Isern, Alexandra R (2002): Linking the oxygen isotope record of late Neogene eustasy to sequence stratigraphic patterns along the Bahamas margin: results from a paleoceanographic study of ODP Leg 166, Site 1006 sediments. Marine Geology, 185(1-2), 95-120 by Silvia Spezzaferri( Computer File )
in English and held by 1 library worldwide
During ODP Leg 166, the recovery of cores from a transect of drill sites across the Bahamas margin from marginal to deep basin environments was an essential requirement for the study of the response of the sedimentary systems to sea-level changes. A detailed biostratigraphy based on planktonic foraminifera was performed on ODP Hole 1006A for an accurate stratigraphic control. The investigated late middle Miocene-early Pliocene sequence spans the interval from about 12.5 Ma (Biozone N12) to approximately 4.5 Ma (Biozone N19). Several bioevents calibrated with the time scale of Berggren et al. (1995a,b) were identified. The ODP Site 1006 benthic oxygen isotope stratigraphy can be correlated to the corresponding deep-water benthic oxygen isotope curve from ODP Site 846 in the Eastern Equatorial Pacific (Shackleton et al., 1995. Proc. ODP Sci. Res. 138, 337-356), which was orbitally tuned for the entire Pliocene into the latest Miocene at 6.0 Ma. The approximate stratigraphic match of the isotopic signals from both records between 4.5 and 6.0 Ma implies that the paleoceanographic signal from the Bahamas is not simply a record of regional variations but, indeed, represents glacio-eustatic fluctuations. The ODP Site 1006 oxygen and carbon isotope record, based on benthic and planktonic foraminifera, was used to define paleoceanographic changes on the margin, which could be tied to lithostratigraphic events on the Bahamas carbonate platform using seismic sequence stratigraphy. The oxygen isotope values show a general cooling trend from the middle to late Miocene, which was interrupted by a significant trend towards warmer sea-surface temperatures (SST) and associated sea-level rise with decreased ice volume during the latest Miocene. This trend reached a maximum coincident with the Miocene/Pliocene boundary. An abrupt cooling in the early Pliocene then followed the warming which continued into the earliest Pliocene. The late Miocene paleoceanographic evolution along the Bahamas margin can be observed in the ODP Site 1006 delta13C values, which support other evidence for the beginning of the closure of the Panama gateway at 8 Ma followed by a reduced intermediate water supply of water from the Pacific into the Caribbean at about 5 Ma. A general correlation of lower sedimentation rates with the major seismic sequence boundaries (SSBs) was observed. Additionally, the SSBs are associated with transitions towards more positive oxygen isotope excursions. This observed correspondence implies that the presence of a SSB, representing a density impedance contrast in the sedimentary sequence, may reflect changes in the character of the deposited sediment during highstands versus those during lowstands. However, not all of the recorded oxygen isotope excursions correspond to SSBs. The absence of a SSB in association with an oxygen isotope excursion indicates that not all oxygen isotope sea-level events impact the carbonate margin to the same extent, or maybe even represent equivalent sea-level fluctuations. Thus, it can be tentatively concluded that SSBs produced on carbonate margins do record sea-level fluctuations but not every sea-level fluctuation is represented by a SSB in the sequence stratigraphic record
Innovations in ocean research infrastructure to advance high priority science ( Book )
1 edition published in 2004 in English and held by 1 library worldwide
Speeding through the 'Valley of Death': More Rapid and Efficient Transition of Instruments and Platforms from Research to Operations ( Book )
1 edition published in 2006 in English and held by 1 library worldwide
This paper focuses on how enhanced cooperation and interaction between the research, operational, and industrial communities can help break down boundaries to better leverage advancements in platforms and sensors and to more rapidly transition instrumentation from the bench top to real-world applications. Existing success stories in the research to operations transition can be used to help establish processes and mechanisms that will enable more rapid and efficient transition of technology through the "valley of death". This paper will also discuss ways to help ensure that the oceanographic tools needed by the operational community are in the visionary pipeline of the research community
The Ocean Observatories Initiative: Wiring the Ocean for Interactive Scientific Discovery ( Book )
1 edition published in 2006 in English and held by 1 library worldwide
The National Science Foundation's Division of Ocean Science has established the Ocean Research Interactive Observatory Networks (ORION) Program to operate and manage existing and future ocean observing sites funded by NSF including those constructed by the Ocean Observatories Initiative (OOI). The OOI is an integrated observatory system with three elements: (1) deep-sea buoys with capabilities appropriate to the experiments they will host with some designs capable of deployment in harsh environments such as the Southern Ocean, (2) a regional electro-optical cabled network consisting of interconnected sites on the seafloor spanning several geological and oceanographic features and processes, and (3) new construction or enhancements to existing facilities leading to an expanded network of coastal observatories. These three components are linked through a forward-looking cyberinfrastructure. This paper will provide an update on current activities related to the OOI Project and the ORION Program
Carbonate and Aluminium accumulation in the central equatorial Pacific Ocean, supplementary data to: Murray, Richard W; Leinen, Margaret S; Isern, Alexandra R (1993): Biogenic flux of Al to sediment in the central Pacific Ocean: evidence for increased productivity during glacial periods. Paleoceanography, 8(5), 651-670 by Richard W Murray( Computer File )
in English and held by 1 library worldwide
We examined the flux of Al to sediment accumulating beneath the zone of elevated productivity in the central equatorial Pacific Ocean, along a surface sediment transect at 135?W as well as downcore for a 650 kyr record at 1.3?N, 133.6?W. Across the surface transect, a pronounced, broadly equatorially symmetric increase in Al accumulation is observed, relative to Ti, with Al/Ti ratios reaching values 3-4 times that of potential detrital sources. The profile parallels biogenic accumulation and the modeled flux of particulate 234Th, suggesting rapid and preferential adsorptive removal of Al from seawater by settling biogenic particles. Normative calculations confirm that most Al is unsupported by the terrigenous fraction. The observed distributions are consistent with previous observations of the relative and absolute behavior of Al and Ti in seawater, and we can construct a reasonable mass balance between the amount of seawater-sourced Al retained in the sediment and the amount of seawater Al available in the overlying column. The close tie between Al/Ti and biogenic accumulation (as opposed to concentration) emphasizes that biogenic sedimentary Al/Ti responds to removal-transport phenomena and not bulk sediment composition. Thus, in these sediments dominated by the biogenic component, the bulk Al/Ti ratio reflects biogenic particle flux, and by extension, productivity of the overlying seawater. The downcore profile of Al/Ti at 1.3?N displays marked increases during glacial episodes, similar to that observed across the surface transect, from a background value near Al/Ti of average upper crust. The excursions in Al/Ti are stratigraphically coincident with maxima in both bulk and CaCO3 accumulation and the excess Al appears to not be preferentially affiliated with opaline or organic phases. Consistent with the similar behavioral removal of Al and 234Th, the latter of which responds to the total particle flux, the Al flux reflects carbonate accumulation only because carbonate comprises the dominant flux in these particular deposits. These results collectively indicate that (1) Al in biogenic sediment and settling biogenic particles is strongly affected by a component adsorbed from seawater. Therefore, the common tenet that Al is dominantly associated with terrestrial particulate matter, and the subsequent use of Al distributions to calculate the abundance and flux of terrestrial material in settling particles and sediment, needs to be reevaluated. (2) The Al/Ti ratio in biogenic sediment can be used to trace the productivity of the overlying water, providing a powerful new paleochemical tool to investigate oceanic response to climatic variation. (3) The close correlation between the Al/Ti productivity signal and carbonate maxima downcore at 1.3?N suggests that the sedimentary carbonate maxima in the central equatorial Pacific Ocean record increased productivity during glacial episodes
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Isern, Alexandra R
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